1. Field of the Invention
The present invention relates generally to baseband ethernet systems and methods, and more particularly to elements, systems and methods for providing baseband ethernet communication over point-to-multipoint shared single line conductor channel topology.
2. Background
Ethernet is a local area network (LAN) technology that connects a variety of computers together in a flexible network system. Ethernet communication generally refers to point-to-point communication within a network of multiple end points. That is, ethernet permits one end point of a network to communicate with another end point of the network, and vice-versa.
Building infrastructure typically incorporates technologies that are commonly known and readily available at the time of construction. For example, FIG. 1 schematically illustrates a typical multi-tenant unit (MTU) building 102 provided with well known cable television (CATV) technology. Generally, the MTU building 102 includes a basement level 103 and a plurality of units (e.g., units 1-M) 104. A unit 104 may be an apartment, a condominium, an office, or the like. The units 104 variously may be located on a plurality of floors (e.g., floors 1-N). For simplicity of illustration and explanation, only the basement 103 and floors 1, 2 and N (including units 1-4, M−1 and M) are illustrated in FIG. 1. The remaining floors and units are structurally and functionally similar to the illustrated floors and units, and therefore are not shown in detail. Each unit 104 may include a television (TV) 106. A TV 106 may include a simple connector that directly receives an input signal. Alternatively, a TV 106 may be provided with an appropriate signal converter box that decodes and/or unscrambles an input signal prior to input to the TV receiver, as is well known in the art. The MTU building 102 is provided with coaxial cable wiring for delivering CATV to the plurality of TVs 106 in respective units 104 of the MTU building 102.
The coaxial cabling 108 in the MTU building 102 is configured in a tree-like, point-to-multipoint topology. In this topology, each unit 104 receives a branch line 110 that is connected via a tap element 112 to a single (common) trunk line 114. For simplicity of illustration, in FIG. 1 each unit is shown with a single branch line 110 and a single TV 106. However, those skilled in the art readily will appreciate that each unit 104 may receive multiple branch lines 110, respectively connecting to multiple TVs. Alternatively, or in addition, a single branch line 110 may include a splitter (not shown), that provides a common signal line to multiple televisions in a single unit 104. The trunk line 114 in turn connects at one end to a service provider entry point 116 of the MTU building 102. The trunk line 114 may be any cable suitable for signal transmission, e.g., 75Ω RG-59 cable. The trunk line 114 further may include an optional bi-directional amplifier 118 provided between the service provider entry point 116 and the first tap element 112, and a terminator (e.g., resistor-to-ground) 120 provided at the end remote from the service provider entry port 116. Although the service provider entry point 116 generally may be located at any location of the MTU building 102, the service provider entry point 116 conveniently may be located in the basement 103 of the MTU building 102, as shown in FIG. 1. In this manner, the coaxial cabling 108 provides a common CATV signal from a single CATV signal source—e.g., service provider entry point 116—located in the basement 103 of the MTU building 102 to each of the plurality of TVs 106 respectively located in a plurality of units 104 of the MTU building 102. This single channel communication coaxial cabling thus may provide low cost delivery of a common CATV signal from a single source to multiple end points/units.
3. Description of Related Art
IEEE 802.3 standards define a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) algorithm for shared media—commonly called ethernet. The IEEE 802.3 standards define connectivity between two transmitter-receivers (transceivers) over various media. For example, under the IEEE 802.3 standards, the 10BASE5 standard (which defines the original standards for CSMA/CD communications) defines ethernet communication standards developed for ethernet over thick coaxial cable; the 10BASE2 standard defines succeeding standards developed for ethernet over thin coaxial cable. In these coaxial cable based standards, the coaxial cable is dedicated to carrying one service—ethernet signals.
Subsequently developed standards under the IEEE 802.3 standards were developed to operate over twisted-wire pairs and fiber optic cable. Such standards include the Fiber Optic Inter-Repeater Link (FOIRL) standard, the 10BROAD36 standard (a broadband system), the 1BASE5 standard (a 1 Mbps twisted-pair wiring system), the 10BASE-T standard (a 10 Mbps twisted pair wiring system), the 10BASE-F standard (fiber optic based systems), and the 10BASE-T, 110BASE-T2, 10BASE-T4 and 10BASE-X standards (twisted-wire pair and fiber optic systems that operate at 100 Mbps). More recent standards developed under the IEEE 802.3 standards include the 1000BASE-X and 1000BASE-T standards (twisted-wire pairs and optic fiber systems that operate at 1000 Mbps).
In ethernet point-to-point communication, one end point (e.g., an originating end point) generally may be referred to as the master, and the other end point generally may be referred to as the client or slave. In operation, the master may define and transmit a master clock (pulse signal) to the slave; in transmitting a response to the master, the slave may synchronize with the master by recovering (also known as slaving off of or timing off of) the master clock transmitted from the master. In a typical ethernet system, however, all end points generally have the same priority, and each end point may perform point-to-point communication with multiple end points of the network over a given period of time.
As noted above, recently developed IEEE 802.3 standards define ethernet communication standards over fiber optic or twisted pair wiring, e.g. two or four twisted pair wirings; these media permit high speed, full-duplex communication between a master and slave—that is, continuous communication in both directions between the master and the slave. In this manner, communications by any ‘master’ or ‘slave’ generally may be sequential or simultaneous.
Coaxial cabling as illustrated in FIG. 1, which offers only a single conductor channel in a tree-like, point-to-multipoint topology, generally is incompatible with IEEE 802.3 standards signaling. The tree-like, point-to-multipoint configuration of FIG. 1 provides a single communication channel that is shared by all users—that is, each user receives a common signal broadcast over a shared, single communication channel. In this case, the signal is broadcast in a single direction downstream over the shared channel. In this manner, a signal may be continuously broadcast from a single source to multiple end points—in this example, a cable TV signal (CATV) may be broadcast over coaxial cable from a single source (service provider entry point) to multiple television sets located in respective multiple units of the MTU building. IEEE 802.3 standards generally cannot be implemented directly on the cable plant of FIG. 1 for at least the following reasons:
1). End points often are isolated from each other through high loss tap elements and cannot reliably detect the presence/absence of communication traffic on the trunk line. For example, a tap element may introduce a 2 dB signal loss in a direction of the trunk line 114 and a 30 dB signal loss across a trunk-branch line connection.
2). Ethernet speeds higher than 10 Mbps utilize continuous transmission protocol. If no data is present, then end points typically transmit idle signals. Idle signals from non-transmitting end-points may interfere with a data signal from a transmitting end-point.
3). CSMA/CD assumes that all end points have equal priority. However, in a topology as shown in FIG. 1, data rates required in the downstream direction (“to” the end points) may be significantly higher than data rates required in the upstream direction (“from” the end points). Particularly in pre-existing applications, it also may be desirable to maintain pre-existing transmission functionality in the downstream direction simultaneously broadcast to all end points (e.g., CATV).
Much infrastructure built over the past few decades does not incorporate ethernet technologies that developed rapidly over the same period of time. Where an MTU building is not pre-wired with fiber optic or data-grade twisted pair wire cabling, it cannot be up-graded to use IEEE 802.3 ethernet to deliver access to broadband services to a plurality of individual units without significant investment in rewiring. A simple ethernet upgrade for preexisting infrastructures is needed.